In recent years, we have been witnessed a rapid advancement of the optical access and local area networks driven by ever growing bandwidth demand, and fundamental inability of the competing technologies, e.g. those based on twisted copper, coaxial cable or wireless transmission, to deliver. Accordingly, transmission over optical fiber has emerged as a universal means for communications, from long-haul to metropolitan area to broadband access networks, resulting in an explosion of optical Internet and convergence of different media streams (e.g. data, voice, and video) into Internet Protocol data delivered in the optical domain right to the end user. Within optical access optical fiber provides a future proof solution to the “last mile” bottleneck, which not only dramatically increases the network capacity, but also eliminates costly transitions from optical into electrical domain (and vice versa). Within local area, metropolitan area, and wide area networks (LAN, MAN, and WAN) optical fiber similarly provides scalable networks exploiting the same wavelength division multiplexing (WDM) techniques atop time division multiplexing at 2.5 Gb/s and 10 Gb/s (OC-48/OC-192) as long-haul networks with 4, 8, 16, 32, 48, or 64 wavelengths for example although expansion by discrete wavelengths is possible.
Such networks exploit a variety of architectures including, but not limited to, point-to-point, linear (also referred to as bus), ring, star, tree and mesh as well as unidirectional traffic per fiber (multiple fibers) and bidirectional traffic per fiber as well as TDM, Coarse WDM (CWDM), and Dense WDM (DWDM) techniques. Linear networks are typically employed in long-haul networks as are mesh networks and the associated fully-connected networks. Ring networks typically appear in LANs, MANs, WANs and tree networks are exploited in fiber-to-the-home/curb/premises (FTTH/FTTC/FTTP) etc (commonly generalized to FTTx). These logical classifications of network topologies describe the path that the data takes between nodes being used as opposed to the actual physical connections between nodes. Logical topologies are often closely associated with Media Access Control (MAC) methods and protocols which in most instances can also be dynamically reconfigured by exploiting routers and/or switches.
These optical networks form therefore the network fabric that provides consumers today with high speed Internet access, on-demand audiovisual content distribution, unlimited simple message service (SMS), etc such that wireless and wired electronic devices for communications, entertainment, and commercial applications have become essentially ubiquitous. As a result of all the stored content terms such as “server farms” and “data centers” have become part of the language representing locations where not tens but hundreds and thousands of computer servers and storage drives (hard drives) are co-located to support the storage and distribution of data on the Internet. “Server farms” and “data centers” exploiting optical networks internally are part of what are now referred to as Enterprise Optical Networks which exploit in addition to other elements Network-Attached Storage (NAS) and Storage Area Networks (SANs) designed to the demands of the application and not generalized computing applications. A NAS device is a server dedicated to nothing more than file sharing and which allows more hard disk storage space to be added to a network that already utilizes servers without shutting them down for maintenance and upgrades. With a NAS device, storage is not an integral part of the server, but rather the server handles all of the processing of data which one or more NAS devices deliver to it and to the user. A NAS device does not need to be located within the server but can exist anywhere in a network, typically a LAN, and can itself be made up of multiple networked NAS devices. A SAN is a high-speed sub-network of shared storage devices where each storage device contains nothing but a disk or disks for storing data. Ideally, a SAN's architecture should make all storage devices available to all servers on the network it is connected to.
With an estimated 100 billion plus web pages on over 100 million websites, data centers contain a lot of data. With almost two billion users accessing all these websites, including a growing amount of high bandwidth video, it's easy to understand but hard to comprehend how much data is being uploaded and downloaded every second on the Internet. At present the compound annual growth rate (CAGR) for global IP traffic between users is between 40% based upon Cisco's analysis (see http://www.cisco.com/en/US/solutions/collateral/ns341/ns525/ns537/ns705/ns827/white_paper_c11-481360_ns827_Networking_Solutions_White_Paper.html) and 50% based upon the University of Minnesota's Minnesota Internet Traffic Studies (MINTS) analysis. By 2016 this user traffic is expected to exceed 100 exabytes per month, over 100,000,000 terabytes per month, or over 42,000 gigabytes per second. However, peak demand will be considerably higher with projections of over 600 million users streaming Internet high-definition video simultaneously at peak times.
All of this data will occur between users flow via data centers or users accessing content in data centers and accordingly between data centers and within data centers these IP traffic flows must be multiplied many times to establish the true total IP traffic flows. Data centers are filled with tall racks of electronics surrounded by cable racks where data is typically stored on big, fast hard drives and computer servers take requests and move the data using, today, fast electrical switches to access the right hard drives. At the periphery of these data centers routers connect the computer servers to the Internet. At the same time as these increasing demands evolving applications such as cloud computing are increasing where computing platforms are no longer stand alone systems but homogenous interconnected computing infrastructures hosted in massive data centers known as warehouse scale computers (WSC) which provide ubiquitous interconnected platforms as a shared resource for many distributed services with requirements that are different to the traditional racks/servers of data centers. As if this was not hard enough evolving business practices, business models, and user expectations for continual price erosion, if not elimination, in the cost per bit transferred and/or stored.
Accordingly, there is a drive for cost-effective yet scalable ways of interconnecting data centers and WSCs internally and to each other so that they and the telecommunication networks can meet the challenge of exponentially increasing demands for bandwidth and speed without dramatically increasing the cost and power of the infrastructure. At the same time expectations of low or no latency in accessing content provide additional pressure. Accordingly data center interconnections, wherein for simplicity we encompass WSCs, NAS, San, server farms as well as traditional data centers within the term data center, have become a critical element in the overall performance of the Internet and the myriad of commercial, financial, and personal applications exploiting it. Fiber optic technologies already play critical roles in data center operations and will increasingly as the goal is to move data as fast as possible, with the lowest latency, with the lowest cost, with the lowest power consumption, and the smallest space consumption. Accordingly, Gigabit Ethernet is too slow and whilst 10 Gb/s solutions such as Ethernet, Fiber Channel, and Intel's LightPeak for example are deployed they are limited. Already Fiber Channel is moving to 16/20 Gb/s and Ethernet is headed for 40 Gb/s and 100 Gb/s. At 40 Gb/s and 100 Gb/s the existing and emerging standards call for multiple 10 Gb/s channels run over parallel multimode optical fiber cables or wavelength division multiplexed (WDM) onto a singlemode fiber. The multimode optical fiber links typically require 8 fibers for 40 Gb/s, represent 4×10 Gb/s in each direction, and 20 fibers for 100 Gb/s, representing 10×10 Gb/s in each direction. With respect to standards then these define a 100 m/150 m reach for 100 GBASE-SR10 links exploiting OM3/OM4 multimode optical fibers respectively. In contrast a 10 km reach is defined for 100 GBASE-LR4 Single Mode Fiber (SMF) links as well as other telecom legacy solutions such as the 10×10 G MSA. The 10×10 G MSA also includes proposed standards for 40 km links.
However, whilst data transmission speeds are increasing such that a given block of information is transmitted within a shorter period of time these evolving systems do not address latency, the time between a request for data being made and the data being provided, nor network failures that can increase latency. Typically, these optical networks either exploit an architecture such as linear, bus, or ring wherein the latency between any two nodes on the network is dependent upon both their distances from the network access points and the relative location of these network access points on the network or a star network wherein latency is driven by their distances from the core and the ability of the central switching fabric to route the data from one “arm” of the network to another. Whilst speed, cost, and some latency have been addressed by exploiting fiber optic links for the “arms” of the network the central switching fabric remains exploiting large electronic cross-connects in order to handle the link capacity.
Optical switching fabrics have to date been primarily focused to space switching applications, e.g. protection, fail-over, and reconfigurable add-drop multiplexers, with switching speeds of the order of milliseconds rather than the nanoseconds and picoseconds necessary to provide switching at the level of frames or other blocks within the data. Whilst, optical switch designs for operation at these timescales exist, e.g. lithium niobate, gallium arsenide, and indium phosphide based photonic circuits, the costs, performance, and scalability of these have limited their deployment in anything other than demonstrations and experimental test-beds. However, it would be evident that latency can be reduced if the data from one node was distributed to all nodes simultaneously rather than being routed through a ring, linear, bus, mesh network or core electronic router.
According to embodiments of the invention the inventors present architectures based upon all-optical passive optical networks, which they refer to as passive optical cross-connection networks (POCXN), that support such a distributive approach to latency reduction as well as protocols relating to their deployment. Beneficially, such POCXN concepts exploit optical components already supported by high volume manufacturing techniques.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.